What causes algae growth in my pool? Understerstanding nitrates and your in-ground pool.

Green Algae filled inground pool

Unfortunately there is much more to taking care of a swimming pool than pouring in some chlorine from time to time.

Numerous factors, such as weather, outside conditions and chemicals used to help maintain a lawn can drastically impact the clarity of a pool.

Nitrates, formed when nitrogen combines with oxygen,  increase the sanitizer demand in the water, meaning the chlorine has to work harder, resulting in rapid depletion of the chlorine tablets or alternative sanitizers.

One of the most common symptoms to help diagnose the presence of nitrates in the water is a clear pool, but the free chlorine residual is constantly reading low, or a perfectly balanced pool that can’t seem to rid itself of algae.

While the pool chemistry may be correct, the presence of nitrates in the water can spark algae growth, making a swimming pool look more like a swamp.

Even if common sources of nitrates aren’t used in your backyard, such as lawn fertilizer, a windy day can drift the elements in your pool from a neighbor’s house a few blocks away.

Other ways nitrates can be introduced to the pool are from human waste, decaying plant life, rain or leaves.

While nitrates don’t specifically turn a pool green, they act like food for algae, a plant that is constantly trying to grow in pools.

If a pool doesn’t have a proper chemical balance and then nitrates are introduced to the water, turning the pool clear again can become a challenge.

Any pool with a nitrate level below 10 parts per million should be able to control algae growth with normal chemical maintenance.

A pool above 10 parts per million should be adding additional algaecide weekly to prevent an algae bloom in the pool. If the pool has 30 or more parts per million, then a chemical treatment is necessary to reverse the effects of nitrates.

If a pool has a nitrate level of 30 parts per million or above, it is recommended to drain approximately 15 percent of the pool water and then refill using hose water.

To determine if nitrates are a problem in your pool, you can either bring a water sample in to Pool Town or purchase testing strips to see if nitrates are really at the root of the problem.

Again, proper chemical maintenance of the water is the best preventative for neutralizing the effects of nitrates in a pool.

Here are a few tips to help prevent nitrates from becoming a problem in your pool.

  1. Maintain proper pH balance, between 7.4-7.6
  2. Ensure the chlorine is always between 2-4 parts per million
  3. Shock the pool and algaecide weekly
  4. Always have all swimmers rinse off before entering the pool
  5. Consult with a Pool Town professional for products to help reduce the effects of nitrates in the pool